Nature of Cementing Materials in Ortstein Horizons of Selected Florida Spodosols: II. Soil Properties and Chemical Form(s) of Aluminum
- F. Y. Lee,
- T. L. Yuan and
- V. W. Carlisle
Possible differences in soil characteristics between ortstein and nonortstein Spodosols were studied. Organic C, fine particles (silt plus clay), and extractable Al by dithionite-citrate, pyrophosphate, acid NH4 oxalate, and NaOH were all higher in Bh than other horizons, except silt plus clay contents in Btg horizons of the St. Lucie County soils. While dithionite-citrate-extractable Si was higher at the surface, larger amounts of Fe seemed to occur in lower horizons. Both contents were much lower than extractable Al with the exception of Si in the A and E horizons. Quartz, gibbsite, kaolinite, and hydroxy-Al interlayered vermiculite were dominant clay-size minerals. In general, no consistent differences were found in soil properties between the paired ortstein and nonortstein Spodosols except that the ortstein horizons contained more clay and more extractable Al. The cementing materials were shown to dissolve in reagents commonly used for Al and Fe extractions. The dithionite-citrate reagent was the most effective extractant. The amounts of extractable Al and Fe by dithionite-citrate, acidic oxalate, and NaOH were small after the ortstein samples were treated with pyrophosphate. These findings suggested that Al in the cementing materials was likely in organic complex form. Ratios of pyrophosphate-extractable Al to oxalate-extractable Al and the percentage of maximum Al-organic complexes supported this assumption. Higher fulvic-C contents and higher fulvic-C to humic-C ratios in ortstein than in nonortstein spodic horizons indicated the complex probably was an Al-fulvate form.
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